The reason that I asked is that, if Heir One was a tenant in common co-owner, then the will becomes relevant since probate would be needed to transfer the deceased's ownership interest to Heir One. And, if there is probate, then any assets are fair game for legitimate creditors.
If Heir One was a co-owner with right of survivorship, then the transfer of the deceased's interest is a non-probate or non-testamentary transfer. Some non-probate transfers could be subject to recovery by legitimate creditors.
Take this for what it is worth because I only skimmed Missouri's non-testamentary provisions and the article referenced below while waiting for your reply. But I believe that real property transferring by right of survivorship would be exempt from recovery by creditors. Here is the chapter of MO statutes dealing with non-probate transfers:
http://www.moga.mo.gov/statutes/C461.HTM
And here is an article from the Journal of the Missouri Bar on that topic:
http://www.mobar.org/uploadedFiles/H...-10/estate.pdf
(Another possibility that I did not think about is a transfer by way of a beneficiary deed.)